The present invention relates to improvements in brake assemblies particularly for use in machine and motor vehicle applications.
There is an increasing worldwide concern for improved standards of machine and motor vehicle operating safety as well as the prevention of environmental damage. These concerns have highlighted problems with conventional xe2x80x9copen-to-atmospherexe2x80x9d brakes. An enclosed fluid immersed brake arrangement as disclosed, for example, in Australian Patent No. 659227 and International Patent Application No. PCT/AU95/00529 has provided an answer to many of these concerns. The brake configurations disclosed in these earlier patent applications utilise conventional pot type cylinders in conventional calliper arrangements. One drawback, however, with pot style cylinders is that they do not lend themselves for convenient layout designs for high torque/small diameter brakes of 300 mm or smaller, or to larger diameter high torque brakes of 400 mm or larger. In the past, annular cylinder designs have been utilised to satisfy the high torque small diameter and larger diameter brake calliper applications. A drawback to the utilisation of such annular cylinder brakes has been that an annular piston arrangement has only been offered as either a hydraulic apply brake or a spring apply hydraulic brake. The former arrangements being unsuitable as a park brake and the latter having drawbacks when utilised as a service brake. A further disadvantage associated with annular cylinder brakes is the difficulties associated with manufacturing same and a requirement for symmetrical placement of the brake pad sets.
An objective therefore is to provide a brake arrangement which will overcome or minimise the drawbacks associated with current brake arrangements. A particularly preferred objective of the present invention is to provide a brake arrangement for an enclosed fluid immersed brake configuration as shown in International Patent Application No. PCT/AU95/00529 which will provide an effective park/emergency braking facility and a service brake facility.
Accordingly, the present invention provides a brake arrangement including a rotatable disc rotor, at least one friction pad adapted for movement towards a braking surface of the disc rotor to provide a braking effect thereon, first brake activating means to provide a park/emergency brake facility operable selectively to urge said one friction pad towards said braking surface of the disc rotor, and second brake activating means to provide a service brake facility selectively operable independently of said first brake activating means to urge said one friction pad towards said braking surface of the disc rotor.
According to a further aspect, the present invention provides a brake arrangement including a rotatable disc rotor, at least one friction pad adapted for movement towards a braking surface of the disc rotor to provide a braking effect thereon, first brake activating means to provide a park/emergency brake facility operable selectively to urge said one friction pad towards said braking surface of the disc rotor, second brake activating means to provide a service brake facility selectively operable independently of said first brake activating means to urge said one friction pad towards said braking surface of the disc rotor, and third means normally acting to prevent said first brake activating means from urging said one friction pad towards said braking surface of the disc rotor. One, two or more said friction pads are provided at circumferentially spaced locations around said rotatable disc rotor, at least two and preferably all of said friction pads being moved simultaneously and selectively by either said first or second brake activating means.
Conveniently, said first brake activating means is adapted to provide a substantially constant force which is transmitted to said at least one friction pad unless countered by said third means. Preferably the substantially constant force provided by said first brake activating means is provided by spring means acting on a piston. Preferably, said second brake activating means includes a pressurised hydraulic fluid selectably supplied to a first piston means arranged to transmit an urging force to said at least one friction pad. Preferably, said third means includes a pressurised hydraulic fluid selectably supplied to a second piston means to produce a counter force to the spring force applied by the spring means to said second piston means. In one preferred embodiment, said first piston means includes an annular piston. In this preferred embodiment the second piston means may also be an annular piston. In a second preferred embodiment, said first piston means may be formed by one or more individual cylinders. In this embodiment, the second piston means may also be formed by one or more individual cylinders. Conveniently, said second piston means is comprised by individual cylinders located on either side of a central cylinder for said first piston means.